Compositions for polishing aluminum/copper and titanium in damascene structures

ABSTRACT

The invention provides compositions and methods for planarizing or polishing a substrate. The composition comprises an abrasive consisting of alumina particles optionally treated with a polymer, an α-hydroxycarboxylic acid, an oxidizing agent that oxidizes at least one metal, polyacrylic acid, optionally, a calcium-containing compound, optionally, a biocide, optionally, a pH adjusting agent, and water. The method uses the composition to chemically-mechanically polish a substrate.

BACKGROUND OF THE INVENTION

Integrated circuits are made up of millions of active devices formed inor on a substrate, such as a silicon wafer. The active devices arechemically and physically connected into a substrate and areinterconnected through the use of multilevel interconnects to formfunctional circuits. In one manufacturing process, a dielectricsubstrate is patterned by a conventional dry etch process to form holesand trenches for vertical and horizontal interconnects. The patternedsurface is then optionally coated with a diffusion barrier layer and/oran adhesion-promoting layer, followed by deposition of a metal layer tofill the trenches and holes. Chemical-mechanical polishing (CMP) isemployed to reduce the thickness of the metal layer, as well as thethickness of the diffusion barrier layer and/or adhesion-promotinglayer, until the underlying dielectric layer is exposed, thereby formingthe circuit device.

One way to fabricate planar metal circuit traces on a silicon dioxidesubstrate is referred to as the damascene process. In accordance withthis process, the silicon dioxide dielectric surface having optionally alayer of silicon nitride deposited thereon is patterned by applying aphotoresist, exposing the photoresist to irradiation through a patternto define trenches and/or vias, and then using a conventional dry etchprocess to form holes and trenches for vertical and horizontalinterconnects. The silicon nitride functions as a “hard mask” to protectthe silicon dioxide surface that is not part of the trenches and/or viasfrom damage during etching. The patterned surface is coated with anadhesion-promoting layer such as titanium or tantalum and/or a diffusionbarrier layer such as titanium nitride or tantalum nitride. Theadhesion-promoting layer and/or the diffusion barrier layer are thenover-coated with a metal layer. Chemical-mechanical polishing isemployed to reduce the thickness of the metal over-layer, as well as thethickness of any adhesion-promoting layer and/or diffusion barrierlayer, until a planar surface that exposes elevated portions of thesilicon nitride surface is obtained. The vias and trenches remain filledwith electrically conductive metal forming the circuit interconnects.

Tungsten and copper have been increasingly used as the electricallyconductive metal. However, aluminum, which has been used in earliergeneration processes to fabricate circuit interconnects via subtractiveprocesses such as etching techniques, is now under consideration for usein damascene processes. The combination of aluminum and titanium offerspotentially lower resistivity than other metal/barrier layercombinations, with corresponding potential improvement in circuitperformance. However, compositions useful in the chemical-mechanicalpolishing of aluminum typically exhibit considerably lower removal ratesin the polishing of underlying titanium. Thus, the use of such polishingcompositions in aluminum damascene fabrication processes to polishaluminum as well as titanium require the overpolishing of aluminumremaining in circuit lines, thereby resulting in considerable dishing ofthe lines. There remains in the art a need for improved compositions andmethods for the chemical-mechanical polishing of substrates comprisingaluminum as a conducting material and titanium as a barrier material.

BRIEF SUMMARY OF THE INVENTION

The invention provides a chemical-mechanical polishing composition forpolishing a substrate. The chemical-mechanical polishing compositioncomprises, consists essentially of, or consists of (a) an abrasiveconsisting of alumina particles optionally treated with a polymer, (b)an α-hydroxycarboxylic acid, (c) an oxidizing agent that oxidizes atleast one metal, (d) about 0.01 wt. % to about 0.2 wt. % polyacrylicacid, (e) optionally, a calcium-containing compound, (f) optionally, abiocide, (g) optionally, a pH adjusting agent, and (h) water, whereinthe polishing composition has a pH of about 2 to about 6.

The invention further provides a method of chemically-mechanicallypolishing a substrate, which method comprises (i) contacting a substratewith a polishing pad and a chemical-mechanical polishing compositioncomprising, consisting essentially of, or consisting of (a) an abrasiveconsisting of alumina particles optionally treated with a polymer, (b)an α-hydroxycarboxylic acid, (c) an oxidizing agent that oxidizes atleast one metal, (d) about 0.01 wt. % to about 0.2 wt. % polyacrylicacid, (e) optionally, a calcium-containing compound, (f) optionally, abiocide, (g) optionally, a pH adjusting agent, and (h) water, whereinthe polishing composition has a pH of about 2 to about 6, (ii) movingthe polishing pad relative to the substrate with the chemical-mechanicalpolishing composition therebetween, and, (iii) abrading at least aportion of the substrate to polish the substrate.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a chemical-mechanical polishing composition forpolishing a substrate. The polishing composition comprises, consistsessentially of, or consists of (a) an abrasive consisting of aluminaparticles optionally treated with a polymer, (b) an α-hydroxycarboxylicacid, (c) an oxidizing agent that oxidizes at least one metal, (d) about0.01 wt. % to about 0.2 wt. % polyacrylic acid, (e) optionally, acalcium-containing compound, (f) optionally, a biocide, (g) optionally,a pH adjusting agent, and (h) water, wherein the polishing compositionhas a pH of about 2 to about 6.

The polishing composition contains an abrasive consisting of aluminaparticles. Preferably, the alumina is fumed alumina or a non-fumedα-alumina. The abrasive particles typically have an average particlesize (e.g., average particle diameter) of about 20 nm (e.g., about 30 nmor more, about 40 nm or more, about 50 nm or more, or about 75 nm ormore). The abrasive particles typically have an average particle size ofabout 500 nm or less (e.g., about 400 nm or less, about 300 nm or less,about 250 nm or less, or about 200 nm or less). Fumed alumina generallyis in the form of aggregates of primary particles, which aggregates arenot easily degraded into individual primary particles withoutsignificant energy inputs. While the primary particles generally arespherical, the aggregates are chain-like structures of the primaryparticles and generally are not spherical. Non-fumed α-alumina is acrystalline form of alumina and typically does not form aggregates.Particle size refers to the diameter of the smallest sphere thatencloses the particle.

The polishing composition can comprise any suitable amount of alumina.Typically, the polishing composition comprises about 0.01 wt. % or more(e.g., about 0.05 wt. % or more, or about 0.1 wt. % or more) of alumina.Preferably, the polishing composition comprises about 2 wt. % or less(e.g., about 1 wt. % or less, or about 0.75 wt. % or less) of alumina.Even more preferably, the polishing composition comprises about 0.01 wt.% to about 2 wt. % (e.g., about 0.05 wt. % to about 1 wt. %, or about0.1 wt. % to about 1 wt. %, or even about 0.1 wt. % to about 0.75 wt. %)of alumina.

At least a portion of the surface of the alumina, especially when thealumina is α-alumina, can be coated with a polymer. For example, about 5wt. % or more (e.g., about 10 wt. % or more, or about 50 wt. % or more,or substantially all, or all) of the surface of the alumina can becoated with a polymer. The polymer can be any suitable polymer.Preferably, the polymer is an anionic polymer. More preferably, theanionic polymer is poly(2-acrylamido-2-methylpropane sulfonic acid) orpolystyrenesulfonic acid.

When the surface of the alumina is coated with a polymer, the weightratio of the polymer to the alumina is generally about 0.01 or more(e.g., about 0.05 or more, or about 0.1 or more, or about 0.16 or more,or about 0.2 or more), based on the weight of the alumina. Preferably,the weight ratio of the polymer to the alumina is about 3 or less (e.g.,about 2 or less, or about 1 or less). The alumina can be treated with apolymer at any suitable time. For example, the alumina can be treatedwith a polymer in a separate step to prepare pretreated alumina prior toaddition of the pretreated alumina to the other components of thepolishing composition. In another embodiment, the polymer can beseparately added to the polishing composition before, during, or afteraddition of the alumina to the polishing composition. In this regard,the weight ratio of polymer to alumina will be understood to refer tothe total weight of polymer in the polishing composition and is notlimited to polymer bound to the alumina.

The abrasive desirably is suspended in the polishing composition, morespecifically in the water component of the polishing composition. Whenthe abrasive is suspended in the polishing composition, the abrasivepreferably is colloidally stable. The term colloid refers to thesuspension of abrasive particles in the liquid carrier. Colloidalstability refers to the maintenance of that suspension over time. In thecontext of this invention, an abrasive is considered colloidally stableif, when the abrasive is placed into a 100 ml graduated cylinder andallowed to stand unagitated for a time of 2 hours, the differencebetween the concentration of particles in the bottom 50 ml of thegraduated cylinder ([B] in terms of g/ml) and the concentration ofparticles in the top 50 ml of the graduated cylinder ([T] in terms ofg/ml) divided by the initial concentration of particles in the abrasivecomposition ([C] in terms of g/ml) is less than or equal to 0.5 (i.e.,{[B]−[T]}/[C]<0.5). The value of [B]−[T]/[C] desirably is less than orequal to 0.3, and preferably is less than or equal to 0.1.

The polishing composition contains an α-hydroxycarboxylic acid. Theα-hydroxycarboxylic acid can be any suitable α-hydroxycarboxylic acid.Non-limiting examples of suitable α-hydroxycarboxylic acids includelactic acid, α-hydroxybutyric acid, and glycolic acid. Preferably, theα-hydroxycarboxylic acid is lactic acid. The polishing compositioncontains about 0.1 wt. % to about 3 wt. % (e.g., about 0.25 wt. % toabout 2.5 wt. %, or about 0.5 wt. % to about 2 wt. %, or even about 1wt. % to about 2 wt. %) of α-hydroxycarboxylic acid. Theα-hydroxycarboxylic acid can be provided as the free acid or as anysuitable salt thereof.

The polishing composition contains an oxidizing agent. The function ofthe oxidizing agent is to oxidize at least one metal, such as a layer orlayers comprising a metal selected from the group consisting ofaluminum, an alloy of aluminum and copper (i.e., aluminum-copper),titanium, and titanium nitride. The oxidizing agent can be any suitableoxidizing agent. Non-limiting examples of suitable oxidizing agentsinclude hydrogen peroxide, persulfate salts (e.g., ammonium persulfate),ferric nitrate, solid forms of hydrogen peroxide, and combinationsthereof. Solid forms of hydrogen peroxide include sodium percarbonate,calcium peroxide, and magnesium peroxide, which liberate free hydrogenperoxide when dissolved in water. Preferably, the oxidizing agent ishydrogen peroxide.

The polishing composition can contain any suitable amount of oxidizingagent. Typically the polishing composition contains about 0.1 wt. % ormore (e.g., about 0.5 wt. % or more, or about 1 wt. % or more) oxidizingagent. Preferably, the polishing composition contains about 10 wt. % orless (e.g., about 8 wt. % or less, or about 5 wt. % or less) oxidizingagent. More preferably, the polishing composition contains about 0.1 wt.% to about 8 wt. % (e.g., about 1 wt. % to about 5 wt. %) oxidizingagent.

The polishing composition contains polyacrylic acid. The polyacrylicacid typically has a molecular weight of about 2000 or more (e.g., about3000 or more, or about 4000 or more). Preferably, the polyacrylic acidas a molecular weight of about 50000 or less (e.g., about 25000 or less,or about 20000 or less). More preferably, the polyacrylic acid has amolecular weight of about 3000 to about 25000 (e.g., about 4000 to about20000). If the molecular weight of polyacrylic acid is too low, thepolishing composition may not exhibit reduced dishing when used topolish substrates comprising aluminum-copper. If the molecular weight ofpolyacrylic acid is too high, the colloidal stability of the polishingcomposition may be compromised.

Typically, the polishing composition contains about 10 ppm or more ofpolyacrylic acid (e.g., about 25 ppm or more, or about 50 ppm or more,or about 100 ppm or more). Preferably, the polishing compositioncontains about 2000 ppm or less (e.g., about 1000 ppm or less, or about500 ppm or less, or about 400 ppm or less, or even about 300 ppm orless) of polyacrylic acid. More preferably, the polishing compositioncontains about 100 ppm to about 2000 ppm (e.g., about 200 ppm to about1000 ppm, or about 200 ppm to about 600 ppm) of polyacrylic acid.

The polishing composition optionally further contains acalcium-containing compound. When a calcium-containing compound ispresent, the polishing composition typically contains a sufficientamount of the calcium-containing compound to provide about 10 ppm ormore (e.g., about 25 ppm or more, or about 50 ppm or more) of calciumion. Preferably, the polishing composition contains a sufficient amountof the calcium-containing compound to provide about 500 ppm or less(e.g., about 400 ppm or less, or about 300 ppm or less, or about 250 ppmor less, or even about 200 ppm or less) of calcium ion. More preferably,the polishing composition contains a sufficient amount of thecalcium-containing compound to provide about 10 ppm to about 500 ppm(e.g., about 25 ppm to about 250 ppm, or about 50 ppm to about 200 ppm)of calcium ion. Advantageously, the presence of calcium ion provided bythe calcium-containing compound provides for enhancement of the removalrate of titanium layers exhibited by the inventive polishingcomposition. The calcium ion contained in the polishing composition canbe provided by one or more suitable calcium-containing compounds.Preferably, the calcium-containing compound is at least onewater-soluble calcium salt. Non-limiting examples of suitable calciumsalts include calcium acetate and calcium chloride, hydrates thereof,and combinations thereof.

The polishing composition optionally further contains a biocide. Thebiocide can be any suitable biocide, for example an isothiazolinonebiocide. The amount of biocide used in the polishing compositiontypically is about 1 ppm to about 500 ppm, and preferably is about 10ppm to about 200 ppm.

The polishing composition has a pH of about 7 or less (e.g., about 6 orless). Preferably, the polishing composition has a pH of about 1 or more(e.g., about 1.5 or more, or about 2 or more). Even more preferably, thepolishing composition has a pH of about 2 to about 6 (e.g., about 2 toabout 4). The polishing composition optionally comprises pH adjustingagents, for example, potassium hydroxide, ammonium hydroxide,alkylammonium hydroxides, and/or nitric acid. Without wishing to bebound by theory, it is believed that polyacrylic acid is bound to theoxidized surface of an aluminum surface being polished by means ofhydrogen bonds with the result that dishing is reduced. If the pH of thepolishing composition is too high, an insufficient number of acrylicacid subunits in the polyacrylic acid are protonated to provide foreffective binding of the polyacrylic acid to the oxidized surface of thealuminum surface being polished.

When the polishing composition consists essentially or of consists ofthe aforementioned components, the polishing composition typicallyexcludes corrosion inhibitors (e.g., heterocyclic compounds comprisingnitrogen atoms, phosphonic acid and derivatives thereof, and the like)and surfactants (e.g., polymeric compounds other than polyacrylic acidand the polymer used to treat the alumina).

The polishing composition can be prepared by any suitable technique,many of which are known to those skilled in the art. The polishingcomposition can be prepared in a batch or continuous process. Generally,the polishing composition can be prepared by combining the componentsthereof in any order. The term “component” as used herein includesindividual ingredients (e.g., abrasive, oxidizing agent, etc.) as wellas any combination of ingredients (e.g., abrasive, oxidizing agent,α-hydroxycarboxylic acid, polyacrylic acid, etc.).

For example, the α-hydroxycarboxylic acid, oxidizing agent, polyacrylicacid, optional calcium-containing compound, and optional biocide can bedissolved in water by addition of the α-hydroxycarboxylic acid,oxidizing agent, polyacrylic acid, optional calcium-containing compound,and optional biocide to water in any order, or even simultaneously. Theabrasive can then be added and dispersed by any method that is capableof dispersing the abrasive in the polishing composition. If the abrasiveis treated with a polymer, the abrasive can be pretreated with thepolymer prior to addition to the polishing composition. In otherembodiments, the polymer can be added to water with the other componentsprior to, or after, addition of the abrasive. The polishing compositioncan be prepared prior to use, with one or more components, such as theoxidizing agent, added to the polishing composition shortly before use(e.g., within about 1 minute before use, or within about 1 hour beforeuse, or within about 7 days before use). The pH can be adjusted at anysuitable time, and is preferably adjusted prior to the addition of theabrasive to the polishing composition. The polishing composition alsocan be prepared by mixing the components at the surface of the substrateduring the polishing operation.

The polishing composition also can be provided as a concentrate which isintended to be diluted with an appropriate amount of water and typicallythe oxidizing agent prior to use. If the oxidizing agent is a liquid, anappropriate volume of the oxidizing agent can be added to the waterprior to dilution of the concentrate with the water, or an appropriatevolume of the oxidizing agent can be added to the concentrate before,during, or after addition of the water to the concentrate. If theoxidizing agent is a solid, the oxidizing agent can be dissolved in thewater or a portion thereof before dilution of the concentrate with thewater and/or an aqueous solution of the oxidizing agent. A solidoxidizing agent also can be added as a solid to the concentrate before,during, or after dilution of the concentrate with the water to providethe polishing composition. The oxidizing agent can be incorporated intothe polishing composition by any suitable method capable ofincorporating the oxidizing agent into the polishing composition, suchas by mixing.

The polishing composition concentrate can comprise an abrasive,α-hydroxycarboxylic acid, polyacrylic acid, optional calcium-containingcompound, optional biocide, optional pH adjusting agent, and water inamounts such that, upon dilution of the concentrate with an appropriateamount of water and oxidizing agent, each component of the polishingcomposition will be present in the polishing composition in an amountwithin the appropriate range recited above for each component. Forexample, the abrasive, α-hydroxycarboxylic acid, polyacrylic acid,optional calcium-containing compound, optional pH adjusting agent, andoptional biocide can each be present in the concentrate in an amountthat is about 2 times (e.g., about 3 times, about 4 times, or about 5times) greater than the concentration recited above for each componentso that, when the concentrate is diluted with an equal volume of water(e.g., 2 equal volumes water, 3 equal volumes of water, or 4 equalvolumes of water, respectively) and an appropriate amount of oxidizingagent, each component will be present in the polishing composition in anamount within the ranges set forth above for each component. Preferably,the water-soluble components present in the concentrate, such as theα-hydroxycarboxylic acid, polyacrylic acid, optional calcium-containingcompound, optional pH adjusting agent, and optional biocide will bepresent in amounts such that the components are fully dissolved in thewater of the concentrate, and in amounts such that the concentration ofthe water-soluble components in the concentrate, more specifically inthe water of the concentrate, is less than the maximum solubility of thewater-soluble components in the water of the concentrate at ambientconditions (e.g., at a temperature of about 20° C.). Furthermore, theconcentrate can contain an appropriate fraction of the water, along withoptionally some or all of the oxidizing agent, present in the finalpolishing composition in order to ensure that the α-hydroxycarboxylicacid, polyacrylic acid, optional calcium-containing compound, optionalbiocide, and optional pH adjusting agent, are at least partially orfully dissolved in the concentrate, preferably are fully dissolved inthe concentrate.

The invention further provides a method of chemically-mechanicallypolishing a substrate comprising (i) contacting a substrate with apolishing pad and the polishing composition described herein, (ii)moving the polishing pad relative to the substrate with the polishingcomposition therebetween, and (iii) abrading at least a portion of thesubstrate to polish the substrate.

Although the polishing composition of the invention is useful forpolishing any substrate (e.g., an integrated circuit, metals, ILDlayers, semiconductors, and thin films), the polishing composition isparticularly useful in the polishing of a substrate comprising at leastone metal layer comprising aluminum or an aluminum-containing alloy suchas aluminum-copper, at least one metal layer comprising titanium, and atleast one dielectric layer. The titanium can be in the form of titaniummetal, alloys thereof, nitrides thereof, and combinations thereof. Thedielectric layer can be a metal oxide, porous metal oxide, glass,organic polymer, fluorinated organic polymer, or any other suitable highor low-k insulating layer, and preferably is a silicon-based metaloxide. More preferably, the dielectric layer is a silicon oxide layerderived from tetraethylorthosilicate and is referred to herein as“TEOS.” In the context of the invention the term “layer” refers both toa continuous, bulk layer of material having a substantially homogeneoussurface and to a surface comprising the material contained within asurface feature (e.g., a circuit line or a via). Advantageously, theinventive polishing composition allows for a high removal rate foraluminum (e.g., aluminum-copper), while exhibiting a desirableselectivity ratio for the polishing of aluminum versus titanium as wellas a very low dielectric removal rate, which renders the polishingcomposition suitable in a “one step” method of removing both excessaluminum and then underlying titanium to expose the dielectric layer.Moreover, the presence of polyacrylic acid in the inventive polishingcomposition desirably results in substantially less dishing of thesubstrate exhibited by the inventive polishing composition.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

EXAMPLE 1

Two similar sets of substrates, each of which substrates separatelycomprised aluminum-copper, titanium, tantalum, and TEOS, were polishedwith two different polishing compositions (Polishing Compositions 1A and1B). Each of the polishing compositions contained 0.5 wt. % of α-aluminatreated with poly(2-acrylamido-2-methylpropane sulfonic acid), 200 ppmpolyacrylic acid, 14 ppm of Kathon 886 MW biocide, and 3 wt. % hydrogenperoxide, at a pH of 3.5. Polishing Compositions 1A and 1B furthercontained 0.5 wt. % and 1.0 wt. % of lactic acid, respectively.

Following polishing, the removal rates (RR) for aluminum-copper,titanium, and TEOS were determined for each of the polishingcompositions, and the results are summarized in Table 1.

TABLE 1 Polishing Al—Cu RR TEOS RR Composition (Å/min) Ti RR (Å/min) TaRR (Å/min) (Å/min) 1A 4611 1119 263 34 1B 5817 1421 202 28

As is apparent from the results set forth in Table 1, increasing theconcentration of lactic acid in the inventive polishing composition from0.5 wt. % to 1.0 wt. % resulted in an increase in the aluminum-copperand titanium removal rates of approximately 26% for both aluminum-copperand titanium, while the tantalum and TEOS removal rates were reduced byapproximately 34% and 18%, respectively.

EXAMPLE 2

Two similar substrates were prepared by sequentially depositing titaniumand then aluminum-copper onto a patterned TEOS layer. The substrateswere polished with two different polishing compositions (PolishingCompositions 2A and 2B). Each of the compositions contained 0.5 wt. % ofα-alumina treated with poly(2-acrylamido-2-methylpropane sulfonic acid),200 ppm polyacrylic acid, 14 ppm of Kathon 886 MW biocide, and 3 wt. %hydrogen peroxide, at a pH of 3.5. Polishing Compositions 2A and 2Bfurther contained 0.5 wt. % and 1.0 wt. % of lactic acid, respectively.

Following polishing, the dishing was determined for a 50 μm widthisolated line, and the results are summarized in Table 2.

TABLE 2 Polishing Composition Dishing (Å) 2A 122 2B 71

As is apparent from the results set forth in Table 2, increasing theconcentration of lactic acid in the inventive polishing composition from0.5 wt. % to 1.0 wt. % resulted in a decrease in dishing ofapproximately 42% observed for a 50 μm width isolated line.

EXAMPLE 3

Four similar substrates comprising aluminum-copper were separatelypolished for 40 seconds with four different polishing compositions(Polishing Compositions 3A-3D). Each of the polishing compositionscontained 0.5 wt. % α-alumina treated withpoly(2-acrylamido-2-methylpropane sulfonic acid) and 3 wt. % hydrogenperoxide, at a pH of 3.5. Polishing Compositions 3A-3D further containedlactic acid and polyacrylic acid in amounts set forth in Table 3.

Following polishing, the removal rates (RR) for aluminum-copper weredetermined for each of the polishing compositions, and the results aresummarized in Table 3.

TABLE 3 Polishing Lactic Al—Cu RR Composition Acid (wt. %) PolyacrylicAcid (wt. %) (Å/min) 3A 0.5 0.02 4483 3B 0.5 0.06 1130 3C 1.5 0.02 63913D 1.5 0.06 1933

As is apparent from the results set forth in Table 3, increasing theamount of polyacrylic acid from 0.02 wt. % to 0.06 wt. % in a polishingcomposition containing 0.5 wt. % lactic acid resulted in a reduction ofthe aluminum-copper removal rate of approximately 75% (PolishingCompositions 3A and 3B). Increasing the amount of polyacrylic acid from0.02 wt. % to 0.06 wt. % in a polishing composition containing 1.5 wt. %lactic acid resulted in a reduction of the aluminum-copper removal rateof approximately 70% (Polishing Compositions 3C and 3D). Increasing theamount of lactic acid from 0.5 wt. % to 1.5 wt. % in a polishingcomposition containing 0.02 wt. % polyacrylic acid resulted in anincrease in the aluminum-copper removal rate of approximately 43%(Polishing Compositions 3A and 3C). Increasing the amount of lactic acidfrom 0.5 wt. % to 1.5 wt. % in a polishing composition containing 0.06wt. % polyacrylic acid resulted in an increase in the aluminum-copperremoval rate of approximately 71% (Polishing Compositions 3B and 3D).

EXAMPLE 4

Two similar sets of substrates, each of which substrates separatelycomprised aluminum-copper, titanium, and TEOS, were polished with twodifferent polishing compositions (Polishing Compositions 4A and 4B).Each of the polishing compositions contained 0.5 wt. % of α-aluminatreated with poly(2-acrylamido-2-methylpropane sulfonic acid) and 3 wt.% hydrogen peroxide, at a pH of 3.5. Polishing Composition 4A furthercontained 3 wt. % succinic acid. Polishing Composition 4B furthercontained 1.5 wt. % lactic acid.

Following polishing, the removal rates (RR) for aluminum-copper,titanium, and TEOS were determined for each of the polishingcompositions, and the selectivity for aluminum-copper versus TEOS wascalculated. The results are summarized in Table 4.

TABLE 4 Polishing Al—Cu RR TEOS RR Selectivity Composition (Å/min) Ti RR(Å/min) (Å/min) (Al/TEOS) 4A 3788 1304 43 88 4B 4232 1623 38 111

As is apparent from the results set forth in Table 4, PolishingComposition 4B, which contained 1.5 wt. % lactic acid, exhibited analuminum-copper removal rate that was approximately 12% greater and atitanium removal rate that was approximately 24% greater, as compared tothe aluminum-copper and titanium removal rates exhibited by PolishingComposition 4A, which contained 3 wt. % succinic acid. In addition,Polishing Composition 4B exhibited a selectivity for aluminum versusTEOS which was approximately 26% greater than Polishing Composition 4A.

EXAMPLE 5

Three similar sets of substrates, each of which substrates separatelycomprised aluminum-copper and titanium, were polished with threedifferent polishing compositions (Polishing Compositions 5A-5C). Each ofthe polishing compositions contained 0.5 wt. % of α-alumina treated withpoly(2-acrylamido-2-methylpropane sulfonic acid), 0.5 wt. % lactic acid,and 3 wt. % hydrogen peroxide, at a pH of 3.5. Polishing Composition 5Acontained no additional components. Polishing Compositions 5B and 5Cfurther contained 0.02 wt. % and 0.1 wt. % polyacrylic acid,respectively.

Following polishing, the removal rates (RR) for aluminum-copper andtitanium were determined for each of the polishing compositions, and theselectivity for aluminum versus titanium was calculated. The results aresummarized in Table 5.

TABLE 5 Polishing Polyacrylic Al—Cu RR Selectivity Composition Acid (wt.%) (Å/min) Ti RR (Å/min) (Al/titanium) 5A 0 3521 1273 2.8 5B 0.02 39961670 2.4 5C 0.1 1373 1567 0.88

As is apparent from the results set forth in Table 5, PolishingComposition 5B, which contained 0.02 wt. % polyacrylic acid, exhibitedaluminum-copper and titanium removal rates that were approximately 13%and 31% greater, respectively, than Polishing Composition 5A, which didnot contain polyacrylic acid. Polishing Composition 5C, which contained0.1 wt. % polyacrylic acid, exhibited aluminum-copper and titaniumremoval rates that were approximately 61% lower and 23% higher,respectively, than the aluminum-copper and titanium removal ratesexhibited by Polishing Composition 5A.

EXAMPLE 6

Two similar substrates comprising aluminum-copper were polished with twodifferent polishing compositions (Polishing Compositions 6A and 6B).Each polishing composition contained 0.5 wt. % of α-alumina treated withpoly(2-acrylamido-2-methylpropane sulfonic acid), 0.5 wt. % lactic acid,0.02 wt. % polyacrylic acid, and 3 wt. % hydrogen peroxide. PolishingComposition 6A had a pH of 3.5, and Polishing Composition 6B had a pH of8.4.

Following polishing, the removal rates (RR) for aluminum-copper weredetermined for each of the polishing compositions. The results aresummarized in Table 6.

TABLE 6 Polishing Composition Al RR (Å/min) 6A 2795 6B <1800

As is apparent from the results set forth in Table 6, PolishingComposition 6A having a pH of 3.5 exhibited an aluminum-copper removalrate that was at least 1.6 times greater than the aluminum-copperremoval rate exhibited by Polishing Composition 6B having a pH of 8.4.

EXAMPLE 7

Nine similar substrates were prepared by sequentially depositingtitanium and then aluminum-copper onto a patterned TEOS layer. Thesubstrates were then polished with eight different polishingcompositions (Polishing Compositions 7A-7H). Each of the compositionscontained 0.5 wt. % of α-alumina treated withpoly(2-acrylamido-2-methylpropane sulfonic acid), 14 ppm of biocide, and3 wt. % hydrogen peroxide, at a pH of 3.5. Polishing Composition 7A(control) did not contain any additional components. PolishingComposition 7B (invention) further contained 0.02 wt. % polyacrylicacid. Polishing Composition 7C (comparative) further contained 0.02 wt.% polymaleic acid. Polishing Composition 7D (comparative) furthercontained 0.045 wt. % polymaleic acid. Polishing 7E (comparative)further contained 0.001 wt. % polyvinyl alcohol. Polishing 7F(comparative) further contained 0.02 wt. % polyvinyl alcohol. PolishingComposition 7G (comparative) further contained 0.001 wt. %polystyrenesulfonic acid. Polishing Composition 7H (comparative) furthercontained 0.02 wt. % polystyrenesulfonic acid. Two substrates werepolished with Polishing Composition 7B (invention).

Following polishing, the dishing was determined for 10 μm and 50 μmwidth isolated lines, and the results are summarized in Table 7. Theresults reported for Polishing Composition 7B represent the average fortwo polishing experiments.

TABLE 7 Polishing Al RR Dishing, 10 μm line Dishing, 50 μm lineComposition (Å/min) (Å) (Å) 7A (control) 2111 942 545 7B (invention)3000 76 81 7C (comparative) 3281 826 350 7D (comparative) 3088 769 2937E (comparative) 2979 895 402 7F (comparative) 2763 868 410 7G(comparative) 2800 876 351 7H (comparative) 2917 746 224

As is apparent from the results set forth in Table 7, PolishingComposition 7B exhibited dishing on a 10 μm line that was 10% or lessand dishing on a 50 μm line that was 36% or less than dishing exhibitedby the control polishing composition or any of the comparative polishingcompositions.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A chemical-mechanical polishing composition consisting essentiallyof: (a) an abrasive consisting of alumina particles optionally treatedwith a polymer, (b) an α-hydroxycarboxylic acid, (c) an oxidizing agentthat oxidizes at least one metal, (d) about 0.01 wt. % to about 0.2 wt.% polyacrylic acid, (e) optionally, a calcium-containing compound, (f)optionally, a biocide, (g) optionally, a pH adjusting agent, and (h)water, wherein the polishing composition has a pH of about 2 to about 6.2. The polishing composition of claim 1, wherein the abrasive consistsof alumina treated with an anionic polymer.
 3. The polishing compositionof claim 2, wherein the negatively-charged polymer ispoly(2-acrylamido-2-methylpropane sulfonic acid) or polystyrenesulfonicacid.
 4. The polishing composition of claim 1, wherein the polishingcomposition contains about 0.1 wt. % to about 1 wt. % of abrasive. 5.The polishing composition of claim 1, wherein the α-hydroxycarboxylicacid is lactic acid.
 6. The polishing composition of claim 5, whereinthe polishing composition contains about 0.5 wt. % to about 2 wt. % oflactic acid.
 7. The polishing composition of claim 1, wherein theoxidizing agent is selected from the group consisting of ammoniumpersulfate, ferric nitrate, and combinations thereof.
 8. The polishingcomposition of claim 1, wherein the oxidizing agent is hydrogenperoxide.
 9. The polishing composition of claim 1, wherein the polishingcomposition contains about 0.001 wt. % to about 0.05 wt. % of acalcium-containing compound.
 10. The polishing composition of claim 1,wherein the polishing composition has a pH of about 2 to about
 4. 11. Amethod of chemically-mechanically polishing a substrate, which methodcomprises: (i) contacting a substrate with a polishing pad and achemical-mechanical polishing composition consisting essentially of: (a)an abrasive consisting of alumina particles optionally treated with apolymer, (b) an α-hydroxycarboxylic acid, (c) an oxidizing agent thatoxidizes at least one metal, (d) about 0.01 wt. % to about 0.2 wt. %polyacrylic acid, (e) optionally, a calcium-containing compound, (f)optionally, a biocide, (g) optionally, a pH adjusting agent, and (h)water, wherein the polishing composition has a pH of about 2 to about 6,(ii) moving the polishing pad relative to the substrate with thechemical-mechanical polishing composition therebetween, and (iii)abrading at least a portion of the substrate to polish the substrate.12. The method of claim 11, wherein the abrasive consists of aluminatreated with an anionic polymer.
 13. The method of claim 12, wherein thenegatively-charged polymer is poly(2-acrylamido-2-methylpropane sulfonicacid) or polystyrenesulfonic acid.
 14. The method of claim 11, whereinthe polishing composition contains about 0.1 wt. % to about 1 wt. % ofabrasive.
 15. The method of claim 11, wherein the α-hydroxycarboxylicacid is lactic acid.
 16. The method of claim 15, wherein the polishingcomposition contains about 0.5 wt. % to about 2 wt. % of lactic acid.17. The method of claim 11, wherein the oxidizing agent is selected fromthe group consisting of ammonium persulfate, ferric nitrate, andcombinations thereof.
 18. The method of claim 11, wherein the oxidizingagent is hydrogen peroxide.
 19. The method of claim 11, wherein thepolishing composition contains about 0.001 wt. % to about 0.05 wt. % ofa calcium-containing compound.
 20. The method of claim 11, wherein thepolishing composition has a pH of about 2 to about
 4. 21. The method ofclaim 11, wherein the substrate comprises at least one layer ofaluminum, and at least a portion of the aluminum is removed to polishthe substrate.
 22. The method of claim 21, wherein the substrate furthercomprises at least one layer of titanium, and at least a portion of thetitanium is removed to polish the substrate.
 23. The method of claim 21,wherein the substrate further comprises at least one layer of adielectric material, and at least a portion of the dielectric materialis removed to polish the substrate.
 24. The method of claim 11, whereinthe substrate comprises at least one layer of an alloy of aluminum andcopper, and at least a portion of the alloy of aluminum and copper isremoved to polish the substrate.
 25. A method of chemically-mechanicallypolishing a substrate, which method comprises: (i) providing a substratecomprising at least one layer of aluminum, titanium, or an alloy ofaluminum and copper, (ii) contacting the substrate with a polishing padand a chemical-mechanical polishing composition comprising: (a) anabrasive consisting of alumina particles optionally treated with apolymer, (b) an α-hydroxycarboxylic acid, (c) an oxidizing agent thatoxidizes at least one metal, (d) about 0.01 wt. % to about 0.2 wt. %polyacrylic acid, (e) optionally, a calcium-containing compound, (f)optionally, a biocide, (g) optionally, a pH adjusting agent, and (h)water, wherein the polishing composition has a pH of about 2 to about 6,(iii) moving the polishing pad relative to the substrate with thechemical-mechanical polishing composition therebetween, and (iv)abrading at least a portion of the substrate to polish the substrate.26. The method of claim 25, wherein the substrate comprises at least onelayer of aluminum, and at least a portion of the aluminum is removed topolish the substrate.
 27. The method of claim 26, wherein the substratefurther comprises at least one layer of titanium, and at least a portionof the titanium is removed to polish the substrate.
 28. The method ofclaim 26, wherein the substrate further comprises at least one layer ofa dielectric material, and at least a portion of the dielectric materialis removed to polish the substrate.
 29. The method of claim 25, whereinthe substrate comprises at least one layer of an alloy of aluminum andcopper, and at least a portion of the alloy of aluminum and copper isremoved to polish the substrate.